Air cleaners of the oil-bath type, generally similar to the present invention, are old and well-known in the art. One air cleaner of this general type is shown and described in the patent to Lowther, U.S. Pat. No. 2,387,278, issued Oct. 23, 1945. Such air cleaners are commonly used for removing dust from an air stream supplying the carburetor of an internal combustion engine. They commonly impinge a dust-laden air stream traveling at relatively high velocity against an oil washed deflector to cause the air stream to pick up some oil, deposit some dust in the oil bath, and then travel outwardly and upwardly into a vertical filter bed which is at least partially coated with such oil to catch dust traveling in the air stream, some of the oil in the filter bed settling downwardly by gravity and returning to the oil bath only when the air flow stops or is slowed down sufficiently.
As indicated above, many such air cleaners are provided with a generally horizontal pan or deflector below and in alignment with the air inlet to deflect the air stream issuing from the air inlet outwardly and upwardly through a conventional filter mass in which oil picked up by the air stream is deposited, the deflector limiting the amount of oil carried upwardly into the filter mass. The space below the pan or deflector serves as an oil reservoir and collector for dust removed from the air stream by the cleaner. Such prior reservoirs normally have a relatively small volume so that all of the oil will be absorbed by the dust and other solid foreign material in a relatively short time, the small volume being necessary to prevent any of the oil from passing out the outlet of the cleaner and into the internal combustion engine to which the cleaner is attached, something which must be avoided. Due to the relatively small volume of the reservoir, such prior art cleaners can collect only relatively small amounts of dust and other foreign material and must be taken out of service and cleaned at relatively frequent intervals.